1. Field of the Invention
The present invention relates to novel primary particles of amorphous silica composite material, secondary particles of said amorphous silica composite material, shaped bodies thereof and processes for producing them.
2. DESCRIPTION OF THE PRIOR ART
The applicant previously proposed: amorphous silica having a property of shaping without use of a binder or the like and an excellent lightweight property; primary particles of amorphous silica prepared by carbonating calcium silicate crystals and treating the reaction product with an acid, said particles retaining the configuration of calcium silicate crystals as original crystals and having a crystalline appearance; secondary particles of amorphous silica composed of said primary particles randomly three-dimensionally interlocked with one another; and shaped bodies thereof (Japanese Examined Patent Publications Nos. 58,436/1986, 41,849/1988 and 41,850/1988 and U.S. Pat. No. 4,230,765). However, these amorphous silica particles have a property of adsorbing, e.g., water and organic materials such as dyes to an extent which is not invariably satisfactory.
On the other hand, the amorphous silica prepared by decomposing an aqueous solution of sodium silicate with hydrochloric acid, sulfuric acid or like acid or with carbon dioxide gas, namely the so-called silica gel of the wet process type, has an excellent adsorbing property, but suffers the drawbacks of lacking a shapability and having a poor lightweight property.